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J. Agric. Food Chem. 2009, 57, 6596–6602 DOI:10.1021/jf9015416
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Fumigant Antitermitic Activity of Plant Essential Oils and Components from Ajowan (Trachyspermum ammi), Allspice (Pimenta dioica), Caraway (Carum carvi), Dill (Anethum graveolens), Geranium (Pelargonium graveolens), and Litsea (Litsea cubeba) Oils against Japanese Termite (Reticulitermes speratus Kolbe) SEON-MI SEO,†, JUNHEON KIM,†, SANG-GIL LEE,† CHANG-HOON SHIN,§ SANG-CHUL SHIN,† AND IL-KWON PARK*,† †
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Division of Forest Insect Pests and Diseases, Korea Forest Research Institute, Seoul 130-712, Republic of Korea, and §Institute of Environmental Resource Research, Jeju Special Self-Governing Province 690-817, Republic of Korea. These authors contributed equally to this work.
Plant essential oils from 26 plant species were tested for their insecticidal activities against the Japanese termite, Reticulitermes speratus Kolbe, using a fumigation bioassay. Responses varied with source, exposure time, and concentration. Among the essential oils tested, strong insecticidal activity was observed with the essential oils of ajowan (Trachyspermum ammi), allspice (Pimenta dioica), caraway (Carum carvi), dill (Anethum graveolens), geranium (Pelargonium graveolens), and litsea (Litsea cubeba). The composition of six essential oils was identified by using gas chromatographymass spectrometry. The compounds thus identified were tested individually for their insecticidal activities against Japanese termites. Responses varied in a dose-dependent manner for each compound. Phenol compounds exhibited the strongest insecticidal activity among the test compounds; furthermore, alcohol and aldehyde groups were more toxic than hydrocarbons. The essential oils and compounds described herein merit further study as potential fumigants for termite control. KEYWORDS: Plant essential oils; Reticulitermes speratus; antitermitic activity; fumigant; ajowan; allspice; caraway; dill; geranium; litsea; thymol; carvacrol; eugenol
INTRODUCTION
Due to their wood-eating habits, several termite species cause serious damage to houses and wooden structures. Because they remain well concealed, their presence is often undetected until the timber is severely damaged from within and shows surface changes, which typically appear last. Once termites have entered a building, they damage not only wood but also paper, cloth, carpets, and other cellulosic materials. The annual damage to wooden structures and other cellulosic materials by termites has been estimated to exceed U.S. $3 billion worldwide (1). Among termite species, subterranean termites from the genera Reticulitermes and Coptotermes are the most economically important species worldwide (2). The Japanese termite, Reticulitermes speratus Kolbe, is the major termite species distributed throughout Korea, Japan, and China. Recently, in Korea, this pest has caused serious damage to important cultural assets such as temples and palaces. Control of the Japanese termite in Korea is primarily dependent upon continued applications of synthetic pesticides or traditional wood preservatives (3). Although effective, there are *Author to whom correspondence should be addressed (telephone þ82-2-961-2672; fax þ82-2-961-2679; e-mail
[email protected]).
pubs.acs.org/JAFC
Published on Web 07/02/2009
concerns regarding the use of such pesticides leading to environmental pollution and health disorders. To avoid these problems, there have been efforts to use plant essential oils as potential alternatives to currently used termite control agents because they constitute a rich source of bioactive chemicals (4, 5); moreover, they are known to be safe as they are commonly used as fragrances and flavoring agents for foods and beverages (6, 7). Furthermore, plant essential oils are highly volatile and therefore do not leave toxic residues. In this study, we selected 26 commercially available plant essential oils that are widely used as fragrances and flavoring agents; we assessed their fumigant toxicity against adult Japanese termites using fumigation bioassays. MATERIALS AND METHODS
Termites. Japanese termites (Reticulitermes speratus Kolbe) were collected from several damaged pine tree logs at Hongneung arboretum, Seoul, Republic of Korea, from March to September 2007 and 2008. Termite-infested wood moistened with distilled water was kept in plastic cages (604040 cm) at 25 ( 1 °C and 80% relative humidity. Chemicals. Plant essential oils were purchased from Jinarome (USA) (Table 1). Information regarding the chemicals used in this experiment is given in Table 3.
© 2009 American Chemical Society
Article
J. Agric. Food Chem., Vol. 57, No. 15, 2009
Table 1. Plant Essential Oils Tested oil
source of plant
part
origin
ajowan allspice amyris Artemisia afra cabreuva cajeput cananga cardamom carrot seeds caraway clementine copaiva coriander davana dill elemi fokienia frankincense galbanum geranium gurjum hyssop larch lavandin litsea patchouli
Trachyspermum ammi Pimenta dioica Amyris balsamifera Artemisia afra Myrocarpus fastigiatus Melaleuca cajuputii Cananga odorata Elettaria cardamomum Daucus carota Carum carvi Citrus clementina Copaifera reticulata Coriandrum sativum Artemisia pallens Anethum graveolens Canarium luzonicum Fokienia hodgensii Boswellia carterii Ferula galbaniflua Pelargonium graveolens Dipterocarpus turbinatus Hyssopus officinalis Larix europea Lavandula hybrida Litsea cubeba Pogostemon patchouli
seeds berries wood flowering plant wood leaves blossoms seeds seeds seeds rind resin fruits leaves seeds resin wood resin resin leaves resin flowering plant resin flowering plant fruits whole plant
India Jamaica Caribbean South Africa Brazil Indonesia Indonesia Equador France Egypt South Africa Brazil Argenitina India Bulgaria Phillipines Vietnam Ethiopia Iran Reunion Indonesia France Austria France Vitenam Indonesia
Instrumental Analysis. Gas chromatography (GC) analysis was performed using an Agilent 6890N equipped with a flame ionization detector. Retention times for comparison with authentic compounds were measured with a DB-1MS and a HP-INNOWax column (30 m 0.25 mm i.d., 0.25 μm film thickness; J&W Scientific, Folsom, CA). The oven temperature was programmed as follows: isothermal at 40 °C for 1 min, raised to 250 °C at 6 °C/min, and maintained at this temperature for 4 min. Helium was used as the carrier gas at a flow rate of 1.5 mL/ min. To determine the configurations of R-pinene, β-pinene, and limonene, a chiral column;Beta DEX120 (30 m0.25 mm i.d., 0.25 μm; Supelco, Bellefonte, PA);was used. The oven temperature was maintained at 100 °C for 20 min, and the flow rate of the carrier gas was 1.0 mL/min. For the chiral GC separation of carvone, a Beta DEX 225 (30 m 0.25 mm i.d., 0.25 μm; Supelco) was used. The temperature program was as follows: 130 °C for 10 min raised to 200 °C at a rate of 10 °C/min. The carrier gas had a flow rate of 1.0 mL/min. GC-mass spectrometry (GC-MS) analysis was performed on an Agilent 7890A coupled with a 5975C mass selective detector (MSD). A DB-5MS (30 m 0.25 mm i.d., 0.25 μm film thickness; J&W Scientific) was used for the separation of the analytes. The oven temperatures were identical to those used for GC. Helium was the carrier gas, at a flow rate of 1.0 mL/ min. Infrared (IR) spectra were recorded on a Nicolet FT-IR (Thermo Fisher Scientific Inc.) spectrometer. Synthesis. Citronellyl acetate, neryl acetate, 2-phenylethyl acetate, and rose acetate (2,2,2-trichloro-1-phenylethyl acetate) were obtained by acetylation of the corresponding alcohol with acetic acid anhydride and pyridine by using p-toluenesulfonic acid as catalyst in CH2Cl2. The corresponding alcohol of rose acetate, 2,2,2-trichloro-1-phenylethanol, was prepared according to a previously reported method (8). The structure was confirmed by comparison of its mass spectrum with data from the NIST mass spectrum library and the IR spectrum. Neryl acetate: yield, 93.9%; purity, 99.2%; IR (neat, cm-1) 2972 (m), 1743 (s), 1379 (m), 1240 (m), and 1026 (m); GC-MS (m/z, %) 196 (Mþ, 0.1), 154 (2.3), 153 (0.2), 136 (16.9), 121 (22.7), 107 (7.7), 93 (57.7), 80 (21.9), 69 (100), and 53 (10.7). 2-Phenylethyl acetate: yield, 89.6%; purity, >99.0%; GC-MS (m/z, %) 163 (Mþ - H, 0.01), 134 (0.02), 121 (0.2), 105 (11.0), 104 (100), 91 (17.7), 78 (5.5), 77 (5.4), 66 (0.4), and 43 (27.4). Citronellyl acetate: yield:, 98%; purity, 96.5%; GC-MS (m/z, %) 155 (Mþ - OAc, 0.1), 138 (47.3), 123 (74.0), 109 (36.7), 95 (97.6), 81 (100), 69 (96.1), 67 (65.1), 55 (46.3), and 43 (77.7).
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2,2,2-Trichloro-1-phenylethanol: KOH (1.84 g, 33.0 mmol; Wako) was added to a solution of benzaldehyde (3.18 g, 30.0 mmol; TCI) and CHCl3 (4 mL) at 0 °C. The solution was stirred for 1 h at 40-50 °C, and 2% H2SO4 solution was then poured. The solution was diluted with diethyl ether and washed with NaHCO3, H2O, and brine and dried over MgSO4. After purification by SiO2 column chromatography and distillation, 2.44 g of the desired alcohol was obtained (yield, 36.3%; purity, 98.4% based on GC). GC-MS (m/z, %) values were as follows: 224 (Mþ, 0.1), 125 (10.0), 107 (B, 100), 79 (52.7), 77 (32.6), and 51 (9.0). IR (neat, cm-1) values were as follows: 3600-3100 (br s), 3062 (s), 3032 (s), 2980 (s), 1497 (s), 1454 (s), 820 (s), and 700 (s). Rose acetate: yield, 74.5%; purity, >99% based on GC; GC-MS (m/z, %) 266 (Mþ, 0.3), 230 (0.6), 209 (0.7), 190 (2.5), 172 (6.0), 149 (40.0), 125 (4.2), 107 (100), 79 (13.6), and 43 (45.9). Antitermitic Activity. Antitermitic activity was evaluated using a fumigation bioassay. A paper disk (8 mm, Advantec) treated with the essential oil or compound being tested was placed in the bottom lid of a glass cylinder (5 cm diameter10 cm) with a wire sieve fitted 3.5 cm above the bottom; thereafter, the lid was sealed. Ten adult worker termites were placed on the sieve. This prevented the direct contact of the termites with the test plant oils and compounds. Filter paper soaked with water was supplied as food. The insects were maintained at 25 ( 1 °C and 80% relative humidity. The adult termites were considered to be dead if appendages did not move when prodded with a brush. Cumulative mortalities were determined 2 and 7 days after treatment. All treatments were replicated five times. Statistical Analyses. Mortality of termites was transformed to arcsine square root values for analysis of variance (ANOVA). Mean values for treatment data were compared and separated by Scheffe´ test (9). RESULTS
Antitermitic Activity of Plant Essential Oils. When 26 plant essential oils were bioassayed, termite mortalities varied according to the oil type, dose, and exposure time (Table 2). Of these, 6 essential oils, ajowan (Trachyspermum ammi), allspice (Pimenta dioica), caraway (Carum carvi), dill (Anethum graveolens), geranium (Pelargonium graveolens), and litsea (Litsea cubeba), achieved >80% mortality 2 days after treatment at 2 mg/filter paper. Artemisia afra, cajept (Melaleuca cajuputii), cananga (Cananga odorata), cardamom (Elettaria cardamomum), coriander (Coriandrum sativum), elemi (Canarium luzonicum), hyssop (Hyssopus officinalis), larch (Larix europea), and lavindin (Lavandula hybrid) showed >80% antitermitic activity 7 days after treatment. Plant essential oils showing >80% mortality at 2 mg/filter paper were tested at lower concentrations. The insecticidal activity of allspice essential oil was 88% 7 days after treatment at 0.5 mg/filter paper; however, this decreased to 0% at 0.25 mg/filter paper. Antitermitic activities of ajowan, caraway, and litsea were 86, 100, and 96%, respectively, 7 days after treatment at 1 mg/filter paper; however, these decreased to 2, 22, and 2%, respectively, at 0.5 mg/filter paper. Essential oils of dill and geranium produced 92 and 84% insecticidal activities at 1.5 mg/filter paper but showed 76 and 78% mortality at 1 mg/filter paper, respectively. Chemical Analyses of Active Essential Oils. The chemical compositions of the six active essential oils;ajowan (T. ammi), allspice (P. dioica), caraway (C. carvi), dill (A. graveolens), geranium (P. graveolens), and litsea (L. cubeba);are shown in Table 3. Retention indices were obtained using an equation proposed by van Den Dool and Kratz (12). We determined the configurations of R-pinene, β-pinene, and limonene by using a chiral column (Beta DEX120). R-Pinene in litsea essential oil consisted of (S)-(-)-R-pinene (0.51%) and (R)-(þ)-R-pinene (0.71%). Only (R)-(þ)-R-pinene was detected in ajowan oil. Ratios of (þ)-β-pinene and (-)-β-pinene were 0.31 and 0.75% in litsea oil, respectively. Only (þ)-β-pinene was identified in ajowan oil. In the case of limonene, two isomers were identified in ajowan and litsea oils, but only (R)-(þ)-limonene was determined
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Table 2. Fumigant Antitermitic Activity of Essential Oils against Japanese Termite mortality (%, mean ( SEM, N = 5) essential oil ajowan
allspice
amyris Artemisia afra cabreuva cajept extra cananga cardamom carrot seed caraway
clementine copaiva coriander davana dill
elemi fokieniawood frankincense galbanum geranium
gurjum hyssop larch lavandin litsea
patchouli control
concn, mg/filter paper 2 1.5 1 0.5 2 1.5 1 0.5 0.25 2 2 1.5 2 2 1.5 2 1.5 2 1.5 2 2 1.5 1 0.5 2 2 2 1.5 2 2 1.5 1 1.5 2 1.5 2 2 2 2 1.5 1 2 2 1.5 2 1.5 2 1.5 2 1.5 1 0.5 2
2 days
7 days
100.0 aa 72.0 ( 4.9 abcde 18.0 ( 5.8 ghi 0.0 i 100.0 a 94.0 ( 4.0 a 82.0 ( 3.7 abc 20.0 ( 3.2 fghi 0.0 i 10.0 ( 5.5 hi 76.0 ( 7.5 abcd 6.0 ( 2.4 hi 10.0 ( 3.2 hi 24.0 ( 7.5 efghi 0.0 i 18.0 ( 5.8 ghi 0.0 i 52.0 ( 10.2 abcdefgh 2.0 ( 2.0 i 0.0 i 88.0 ( 4.9 ab 64.0 ( 2.4 abcdefg 10.0 ( 6.3 hi 0.0 i 16.0 ( 5.1 ghi 10.0 ( 3.2 hi 78.0 ( 5.8 abc 4.0 ( 4.0 hi 28.0 ( 3.7 defghi 88.0 ( 4.9 ab 28.0 ( 5.8 defghi 0.0 i 0.0 i 0.0 i 0.0 i 2.0 ( 2.0 i 0.0 i 2.0 ( 2.0 i 98.0 ( 2.0 a 44.0 ( 6.0 bcdefghi 22.0 ( 3.7 fghi 6.0 ( 2.4 hi 68.0 ( 3.7 abcdef 26.0 ( 6.8 efghi 38.0 ( 7.3 cdefghi 2.0 ( 2.0 i 34.0 ( 4.0 cdefghi 6.0 ( 2.4 hi 100.0 a 78.0 ( 5.8 abc 42.0 ( 4.9 bcdefghi 0.0 i 2.0 ( 2.0 i 0.0 i
100.0 a 100.0 a 86.0 ( 2.4 abcd 2.0 ( 2.0 i 100.0 a 100.0 a 100.0 a 88.0 ( 5.8 abcd 0.0 i 46.0 ( 7.5 bcdefghi 100.0 a 72.0 ( 4.9 abcdef 72.0 ( 6.6 abcdef 100.0 a 28.0 ( 8.6 fghi 94.0 ( 4.0 ab 8.0 ( 3.7 hi 100.0 a 16.0 ( 4.0 ghi 56.0 ( 4.0 abcdefgh 100.0 a 100.0 a 100.0 a 22.0 ( 5.8 ghi 60.0 ( 3.2 abcdefg 76.0 ( 4.0 abcdef 96.0 ( 2.4 a 42.0 ( 5.8 defghi 44.0 ( 2.4 cdefghi 100.0 a 92.0 ( 3.7 abc 76.0 ( 2.4 abcdef 4.0 ( 2.4 i 86.0 ( 6.8 abcd 32.0 ( 3.7 efghi 28.0 ( 6.6 fghi 32.0 ( 3.7 efghi 30.0 ( 5.5 efghi 98.0 ( 2.0 a 84.0 ( 5.1 abcd 78.0 ( 5.8 abcde 8.0 ( 2.0 hi 100.0 a 64.0 ( 4.0 abcdefg 100.0 a 72.0 ( 8.0 abcdef 94.0 ( 2.4 ab 30.0 ( 7.1 efghi 100.0 a 100.0 a 96.0 ( 2.4 a 2.0 ( 2.0 i 56.0 ( 4.0 abcdefgh 0.0 i
a Means within a column followed by the same letters are not significantly different (P = 0.05, Scheffe test).
in allspice oil. The main components of caraway oil were (S)-(þ)carvone (48.7%), (R)-(þ)-limonene (24.2%), cis-carveol (0.4%), and trans-carveol (0.3%). The most abundant compound in dill oil was (S)-(þ)-carvone (35.56%) followed by (R)-(þ)-limonene (20.21%), myrcene (4.89%), dill ether (4.58%), and p-cymene (2.34%). Ratios of the other compounds were
